TEST FACILITIES CPRICables lab has facilities to undertake type testing of all types of power cables of rating 1.1 kV up to 220 kV

voltage rating and their accessories as per Indian and International standards .In addition the laboratory can

undertake partial discharge test and dielectric loss power factor measurement on current transformers, bushings and

surge arrestors etc.

TESTING/EQUIPMENT FACILITY:-

o  600 kV, 600 KVA series Resonant test set. o 300 kV, 120 KVA Transformer o 100 kV, 20 KVA Partial discharge free test source and associated accessories. o 500 kV, 15 KJ Impulse voltage generator o 2000 Amps Current transformer o Robinson 803 Partial discharge discrimination System o Bonar Model 5 Discharge Detector o Transformer ratio arm bridges, 600 kV Standard capacitor o   High Precision automatic insulation resistance measuring kit. o   500 kV water terminations for testing of EHV cables. o   Splicing machines for preparation of cable insulation samples for physical tests.   

o   Profile projector of magnification upto 100

Products/Apparatus Type of test

Paper/PVC/XLPE/EPR Power  cables of

Voltage rating up to 220 kV

 

 

 Cable Accessories

  

Current Transformers, Bushings, Surge

Arrestors etc up to 220 kV Rating

All type test like partial discharge test, Tan delta

measurement, Conductor Resistance Test, Tensile

Test, Hot Deformation Test, Hot Set test, Shrinkage

Test, Thermal Stability test etc

 All type test like partial discharge test, DC High Voltage

Test, Impulse Test, Load Cycle Test Etc.

  Partial discharge Test, Dielectric Loss Power Factor

Test

Products Standards

PILC  cables up to 33 kV

Elastomeric,& Polymeric insulated Power

cables  up to 220 kV

Aerial bunched cables, Mining Cables

Cable joints & Terminations

Partial discharge testing on instrument

transformers

Partial discharge testing on Surge Arrestors

IS 692, IEC 55-1, BS –6480

IS 7098 Part I,II, & III, IS 1554 Part I.& II, IS 694,  IEC

60227,  IEC 60245, IS 9968 Part I & II,  IEC 60840, IEC

62067 ,IEC 60502 –1,IEC 60502-2, BS 6622,    BS

5467,BS 6346

IS 14255, IS 14494

C-81,IS 13573, IS 13705, IEC 60502-4,VDE 0278- 629,

IEC 60044-1,IEC 60044-2, IEC 60044-3, IS 11322 , IS

3070, IEC 60099-4

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Type Tests• Bending test• PD test amb.• Diel. loss test• Heating cycle test• PD hot and PD amb.• Impulse test hot• AC test• PD amb if not done before• PD test amb • Heat cycle test• PD test amb and PD hot• Impulse test hot• Impulse test amb.• AC test• PD test amb.

Insulating materials Dielectric properties of cable insulation:1. 1.        high insulation resistance2. 2.        high dielectric strength3. 3.        good mechanical properties4. 4.        immune to attacks by acids & alkalies5. 5.        non-hygroscopicCommonly used insulating materials are:a) a)       Oil-impregnated paperb) b)       Vulcanized India rubber(V.I.R)c) c)       Polyvinyl chloride(P.V.C)d) d)       SF6 gase) e)       Cross-linked polythene(XLPC) Void formationVoids (small pockets of air or gas) are formed in the insulation where constituent parts of the cable are expanded and contracted to different extents with heat evolved on load cycles. The stress across the voids is high and breakdown results. Electrostatic stress in a single core cable

The potential gradient is maximum at the surface of the conductor. Potential gradient art any point at a distance x from the centre of the conductor is G= V/ [x ln (R/r)] Where R is the inner radius of the sheath and, and r is the radius of the conductor. Grading of cables a) a)       Capacitance gradingb) b)       Intersheath grading Dielectric loss and loss tangent of a cable

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  The dielectric loss, due to leakage and hysterisis effects in the dielectric, is usually expressed in terms of the loss angle,d: d = 90- f where f is the dielectric power factor angle. Dielectric loss = w C V2 tan d, Where C= capacitance to neutralV= phase voltage A typical value of tan d lies in the range 0.002 to 0.003. In low voltage cables the dielectric loss is negligible, but is appreciable in EHV cables.

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Tests on Electrical Materials

Type Tests – Tests carried out to prove conformity with the specifications. These are intended to prove the general

qualities and design of a given type of manufactured item.

 

Routine Tests-Tests carried out on each part/item manufactured to check parameters (as per requirements0, which are

likely to vary during production.

 

Acceptance Tests- Tests carried out on samples taken at random from offered lot of manufactured item for the purpose

of acceptance of lot.

TYPE TESTS 

No. Type test Purpose

a Tests on conductor

1. 1.        Annealing test (for copper)

2. 2.        Tensile test (for Aluminum)

3. 3.        Wrapping test (for Aluminum)

4. 4.        Resistance test

 

To check softness of wire

To check strength of Al wire

To check hardness of Al wire

To check cross-section of the conductor

b Tests for armouring wires/strips To check electrical , mechanical and chemical

properties of armouring wire/strip

c Test for thickness of insulation and sheath To check capability of insulation to withstand

voltage and its mechanical strength

d Physical test for insulation & sheath  

1. Tensile strength & elongation at break

 

To check mechanical stress and strain during

manufacturing and bending

2. Ageing in air oven

 

To check physical & chemical changes in

insulation due to heat with age

3. Shrinkage test

 

To prevent problem in termination

4. Hot deformation To check resistance against deformation due to

heat & mechanical pressure

5. Loss of mass in air oven To check physical & chemical changes in

insulation due to heat and time

6. Heat shock test To check ability of cable against overheating

7. Thermal stability To check thermal effect

e Insulation resistance test To check uniformities of insulation in dielectric

f High voltage test(Water immersion test) To check ability of cable in water during service

g High voltage test at room temperature To check ability of cable against high voltage

during service

h Flammability test To check flame retardant properties

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OPTIONAL TYPE TESTS

 

No. Optional type test Purpose

a Cold bend test To check effect of low temperature during

bending

b Cold impact test To check effect of low temperature on outer

sheath in terms of hardness & softness

c Armour resistance test (or other than

mining cables

To check electrical properties of armouring

wire/strip

ROUTINE TESTS

 

No. Test Purpose

a Resistance test To check cross-section of the conductor

b High voltage test at room temperature To check ability of cable against high voltage

during service

c Armour resistance test (for mining cables) To check conductivity of armouring materials

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CROSS –LINKED POLYETHYLENE INSULATED PVC SHEATHED CABLES [XLPE from 66 to 220 kV][IS: 7098 (Part-3)-1988]

TYPE TESTS:

 No. Type Test Purpose

a Tests on conductor

1. Annealing Test (for Cu)

To check softness of wire

2. Resistance Test To check cross-section of the conductor

b Physical tests on insulation  

1. Test for thickness & dimensions of insulation To check capability of insulation to withstand

voltage and its mechanical strength

2. Tensile strength & elongation at break To check mechanical stress & strain during

manufacturing & bending

3. Thermal ageing in oven To check physical & chemical changes in

insulation due to heat with age

4. Hot set test To check cross-linking of insulating material

5. Shrinkage test To prevent problem in termination

6.Void & contaminants test To check voids & contaminants

c Resistivity test for semi conducting layers To check resistance of semi-conducting layer

d Test for concentric metallic screen

i) i)         Test for concentric metallic

screen

ii) ii)       Test for concentric copper tape

To check capacity against short circuit

e Thickness of metallic sheath To check capability of insulation to withstand voltage and its mechanical strength

f Tests for armouring material

1. Dimensions

To check that dimensions are within limits

2.Tensile strength & elongation at break To check mechanical stress and strain during

manufacturing and bending

3. Wrapping test To check mechanical strength during bending

4. Resistivity test To check resistance of armouring material

g Physical tests for outer sheath  

1 Measurement of thickness To check mechanical strength

2 PVC Sheath To know the material used

1. Tensile strength & elongation at break To check mechanical stress and strain during

manufacturing and bending

2. Thermal Ageing in air oven 

To check physical & chemical changes in

sheath due to heat with age

3. Loss of mass To check physical & chemical changes in

insulation due to heat and time

4. Heat shock test To check ability of cable against overheating

5. Hot deformation test To check resistance against deformation due

to heat & mechanical pressure

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6. Shrinkage test To prevent problem in termination

  7. Thermal Stability To check thermal effect

3. PE SHEATH To know the material used

  1. Carbon black content To know the % of carbon

  2. Tensile strength & elongation at break before

& after ageing

To check mechanical stress and strain during

manufacturing and bending

  3. Hot deformation To check resistance against deformation due

to heat & mechanical pressure

h Flammability test (for PVC outer sheathed cable

only)

To check flame retardant properties

j Water tightness test To check penetration of water in cable

k 1. Thermal ageing on complete cable sample To check physical &chemical changes in

cable due to heat with age

  2. Tensile strength & elongation at break for

insulation & outer sheath

To check mechanical stress and strain during

manufacturing and bending

  3. Resistivity test for semi- conducting layers To know resistance of semi-conducting layer

m Bending test followed by P. D. test To check bending radius during bending while

installation & handling

n Dielectric power factor measurement at ambient

temperature

To check rupturing capacity & voids

p Dielectric power factor measurement at elevated

temperature

To check impurities & voids

q Load cycle test followed by P.D measurement To check capacity of cable under loading

conditions

r Impulse withstand test followed by HV test To check ability of insulating material to

withstand lightning voltage

NOTES: Tests from (n) to ( r ) shall be performed successively on the same test sample of complete

cable, not less than 10 m length between test accessories

Tests at (p) and (q) may be carried out on different samples.

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OPTIONAL TYPE TEST: 

No. Type Test Purpose

1 Cold impact test for outer sheath To check effect of low temperature on outer sheath in terms of hardness & softness

 ROUTINE TESTS

 

ACCEPTANCE TESTS 

No. Acceptance Test Purpose

1 Measurement of capacitance To check impurities & voids

The following Type Tests will be used as Acceptance Tests: a1,a2, b1, b4,b6,e, g1

The following Routine Tests will be used as Acceptance Tests: b, c

Partial discharge test shall be carried out on full drum length

 SCALE OF SAMPLING

  

No. of Drums in a Lot No. of Drums to be taken as sample

Permissible No. of Defectives

Up to 25 3 0

26 to 50 5 0

51 to 100 8 0

101 to 300 13 1

301 and above 20 1

  

DRUMS FOR EECTRIC CABLES [IS: 10418-1982]The tests under TYPE, ROUTINE and ACCEPTANCE categories are not specified in the Indian Standards. However, the following checks shall be made on DRUMS & their components.CHECKS FOR CONSTRUCTION OF DRUM:

 S.

No.

Description Purpose

1 Mechanical strength (a) Transverse loading test

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No. Routine Test Purpose

a Conductor resistance test To check cross-section of the conductor

b P. D. test To check small voids and cavities in insulation

c HV test To check ability of cable in service

(b) Impact test

(c) Barrel batten test

2 Flange & outside surface Free from protruding materials or Projections or

unevenness capable of damaging the cable/hands

3 Flanges (Main Discs) construction a) For dia. Up to 1600mm- 2 ply OR 3 ply

construction.

b) For dia. Above 1600 mm- 2 full ply OR 3 full ply

plus 1 segmental layer construction

(Segments shall not be less than six)

Width of middle plank (Minimum) For flange dia up to 700mm- 100 mm

Dia 701 mm-1600mm- 150 mm

Dia above 1600 mm- 200 mm

4 Barrel end- supports Shall be complete circular discs or of various

segments. Securely fixed to inside of flanges by

nailing

5 Barrel middle-supports Shall be complete circular construction of

single/two ply layers (at 90 0) OR of various

segments (Only for drums having transverse

above 1000 mm).

6 Stretchers (Core carrier planks) To be provided for drum sizes of 1206 mm and

above

7 Tolerances in mm mm

  Drum flange dia ,up to & including 1600 mm

Above 1600 mm

 

+/- 20

+/-30

  Flange thickness up to & including 1600 mm

Above 1600 mm

 

+/- 06

+/-09

  Barrel dia. up to & including 1600 mm

Above 1600 mm

 

+/- 20

+/-30

  Overall & transverse widths +/- 25

  Barrel battens thickness +/-3

  Stretchers thickness +/-3

  Centre hole dia. with bush 0 to+2

  Centre hole dia. without bush 0 to +5

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